1. Field of the Invention
This invention relates to a recording apparatus for recording information signals on a magnetic recording medium.
2. Description of the Prior Art
Heretofore, there have been proposed and put into practice recording/reproducing apparatus of the kind arranged to have a second signal, which consists of pilot signals of one or a plurality of different frequencies lower than that of a first signal, recorded in superimposition on the first signal; and, in reproducing the record, to adjust the position of reproducing heads with respect to recording tracks on the recording medium, that is, to perform tracking control, by using the reproduced second signal. With the apparatus arranged in this manner, for inserting a different signal into the recorded signal, i.e. for performing an operation called insert recording, there have been known various methods including, for example, such methods as shown in FIGS. 4, 5 and 6 of the accompanying drawings.
In FIG. 4 which illustrates the state of recording tracks obtained in the event of insert recording, a signal A, representing the first signal, and pilot signals, representing the second signal, are recorded in tracks A1 to Ak on a record bearing medium or tape t. Among these tracks, an n number of tracks Ai+1 to Ai+n are to be replaced with tracks B1 to Bn for recording a signal B that is different from the signal A in the event of insert recording.
It is important for such insert recording to secure, first of all, the continuity of joints between the tracks Ai and B1 and between the tracks Bn and Ai+n+1. It is also important to have the signal recorded with adequate quality in the new tracks B1 to Bn. To meet the former requirement, the signal B must be recorded in the tracks B1 to Bn under the tracking control accomplished by means of the pilot signals recorded in the tracks Ai+1 to Ai+n. To meet the latter requirement, the signal A, which is recorded in the tracks Ai+1, to Ai+n must be erased either one by one or several tracks at a time before recording the signal B in the tracks B1 to Bn, by using an erasing head which is arranged to precede a recording head.
For carrying out these operations, in a method of the prior art, the tracking control is performed by reproducing the pilot signal recorded in the applicable part while leaving unerased some portion of the record of that part corresponding to a vertical retrace period not appearing in the picture. FIG. 5 shows insert recording performed by this method. The illustration includes a recording/reproducing head R; and an erasing head E. An arrow X indicates the travelling direction of the tape t. Another arrow Y indicates the shifting direction of the head. A reference symbol C denotes an erased part. Symbols A'i+1, A'i+2, A'i+3 and A'i+4 denote erased parts. An erasing current is cut off only while the erasing head E is passing the unerased part. Then, the pilot signal is reproduced for tracking control when the recording/reproducing head R passes this part.
FIG. 6 is an enlarged view showing the state of the track A'i+4 obtained with recording performed without leaving any guard band. The width WH of the head is arranged to be somewhat wider than a track pitch WP. Therefore, the overlapping width W1 between the adjacent track A'i+3 and the erasing head E obtained at a period T1 within a period T, during which the erasing head E passes through the track A'i+4, differs from the overlapping width W2 between the adjacent track B3 and the erasing head E obtained during another period T2. Therefore, the tracking control cannot be performed during the period T1 during which the overlapping width is at the value of width W1.
Meanwhile, the erasing head E is provided with more than two gaps. As a result, a boundary kb between the tracks B4 and A'i+4 and a boundary kc between the track A'i+4 and an erased part C are not clear, as shown in FIG. 6. Therefore, an effective period for tracking control is shorter than the period of time T1.
The timing at which the erasing head E and the recording/reproducing head R pass the track A'i+4 fluctuates due to some disturbance. Besides, since the period T is determined by the signal B to be newly recorded, the positions of the tracks A'i+1 to A'i+4 fluctuate and deviate on the tape t due to the fluctuation of the signal B and the fluctuation of the shift of the head. These conditions further shortens the period of effective tracking control. Then, such short effective period of tracking control brings about a serious disadvantage against disturbance, noises and drop-out.